U.S. Pat. No. 3,682,378 for a Value Dispensing Mechanism, issued Aug. 8, 1962 to Rouan et. al. and assigned to the assignee of the present invention, discloses a rotary postage value selection mechanism including a plurality of longitudinally translatable rack gears which are individually connected for rotating an associated print wheel via an idler gear fixedly connected to the print wheel.
U.S. Pat. No. 4,050,374 for a Meter Setting Mechanism, issued Sep. 27, 1977 to Check, Jr. and assigned to the assignee of the present invention, discloses a mechanism for selecting postage values which are to be printed by a rotary postage meter. The drive shaft of the drum includes a plurality of selectable racks, each of which is slidably movable in engagement with a different pinion gear, connected to an associated print wheel within the drum, for selectively rotating the print wheel to dispose a printing element or font thereof at the outer periphery of the drum for printing purposes. The value selection mechanism includes a first stepper motor which is operable for selecting one of the racks, and a second stepper motor which is operable for actuating the selected rack for selectively rotating the desired printing element of its associated print wheel to the printing position thereof. An electronic control system (not shown) which is coupled to a keyboard for processing postage value entries made by an operator, selectively drives the respective stepper motors in response to keyboard entries.
Value selection mechanisms of the aforesaid types have from time-to-time become physically damaged with the result that one or more rack gears have become disassociated from an associated print wheel drive gear, with the result that the print wheels may be rotated independently thereof. Whereupon, a postage value can be printed which is different from that which has been selected by means of the associated rack gear. Although the occurrence of such physical damages are immediately apparent to a postage meter user, meters have been known to be continued to be used despite such a malfunction condition, in order to wrongfully print postage values without payment therefor. Of course, since postage meters are required to be physically inspected on a semi-annual basis, and more frequently when Postal Service inspectors, through internal postage indicia inspection controls and accounting practices, suspect that a postage meter is dispensing more postage than has currently been paid for, such physical damages have a short life span due to their inevitably early discovery. Nevertheless, any postage payment losses are rightfully of great concern to the Postal Service and to postage meter manufacturers. As a result, a series of experimental activities with postage meters have been conducted to determine the basic cause, if any, of disassociation of postage selecting racks and print wheels. And, it has been experimentally determined that the majority of the instances in which such disassociations occur are due to a sufficient force being exerted against the print wheel to separate the same from the drive train therefor. Accordingly:
an object of the invention is to provide means for weakening the drive train, between the rack and print wheel of a value setting mechanism, against a force exerted against the print wheel which tends to separate the print wheel from the drive train, in order to cause the drive train to jam in response to the force; PA1 another object is to provide means for permitting distortion of a drive gear upon exertion of a force against a print wheel driven thereby; and PA1 another object is to provide rotary value selection and printing apparatus, including a print wheel drive gear which is weakened, against the exertion of a force against a print wheel which is sufficient to separate the print wheel and the drive gear, to permit the drive gear to distort, in response to the force, in a manner such that the drive gear becomes jammed against rotational movement thereof.